In recent years, a Group III nitride compound semiconductor light-emitting device is widely used in a field of a light-emitting diode (LED) which emits any one of green, blue, and ultra-violet lights and has advantages in reduction in size and weight and longer operating life. Demands on a LED having higher luminous intensity and more excellent efficiency are also increasing. In order to improve luminous intensity and efficiency of a LED, outputting efficiency of the lights which is emitted from the emission layer, or external quantum efficiency, needs to be improved along with increasing internal quantum efficiency. With respect to improving external quantum efficiency, there are known Patent application laid-open No. 2000-196152 and Patent application laid-open No. H5-167101.